My biochemistry and organic chemistry are weak. It seems that there must be a way to chemically distinguish PNA from protein and DNA. Like, some in vitro reaction that would work with PNA but not the others. Can anyone help me figure out what this reaction might be?

edit: The bases are attached to the backbone via amide bonds in PNA. Could these bonds be chemically broken - releasing the bases - in some way, a way that wouldn't relese bases from the phosphodiester backbone in RNA or DNA?